Angiogenesis, the formation on new blood vessels, plays a critical role in a number of physiological and pathological processes, including wound healing, tumor growth, and rheumatoid arthritis (RA). Previously Dr. Koch's lab has shown that the soluble adhesion molecules E-selectin and vascular cell adhesion molecule-1 are present in RA synovial fluid and act as proangiogenic factors. Junctional adhesion molecules (JAMs) are novel members of the Immunoglobulin supergene family that are expressed by various cell types, including endothelial cells, and play critical roles in controlling vascular permeability, leukocyte retention, and trans-endothelial migration. Recent studies have also demonstrated roles for membrane bound JAM-A and JAM-C in mediating angiogenesis. To date, the role of soluble JAMs (sJAMs) in angiogenesis has not been determined. We therefore hypothesize that sJAMs play critical roles in mediating angiogenesis. To test this hypothesis we will (1) examine the role of sJAM-A, -B, and -C in angiogenesis by designing an enzyme- linked immunosorbent assay (ELISA) to determine the levels of sJAMs in normal blood, RA blood, and RA synovial fluid. Once the presence of sJAMs has been demonstrated, we will assess their ability to induce human dermal microvascular endothelial cell (HMVEC) chemotaxis in vitro. We will then determine if sJAMs induce HMVEC tube formation on Matrigel in vitro and in Matrigel plugs in vivo. (2) We will then determine the signaling pathways and receptors by which sJAMs mediate angiogenesis by stimulating HMVECs with sJAMs and examining specific pathways by Western blot and immunofluorescence. (3) Finally, we will determine the mechanisms by which sJAMs mediate angiogenesis by performing HMVEC chemotaxis assays in vitro in the presence and absence of signaling inhibitors. These results will be confirmed using Matrigel tube formation assays in vitro and Matrigel plug assays in vivo with sJAMs in the presence and absence of signaling inhibitors directed against the signaling molecules determined above. PUBLIC HEALTH RELEVANCE: Elucidating the role of sJAMs in angiogenesis and the mechanisms by which they work may provide another route for modulating angiogenesis in tumor growth, cardiovascular disease, and RA.